NC OS on RPCEmu?

Hi all. Apologies if this has been covered before, but can RPCEmu support Acorn’s NC OS?

I have one of the ‘Bush Internet Set Top Box’ devices (model IBX200) which runs NC OS 5.13.
By design, the device does not output any video until the ‘Internet’ button on its keyboard is pressed. After some trial and error with the KeyMapper module, I found that this ‘internet’ button is mapped to low-level internal key number 215.
I speculated that the only requirement for booting the OS on RPCEmu would be to simulate a ‘number 215’ key press, so I saved the ROM image to a Zip disk and had a try, but RPCEmu just freezes with a red screen, even when the emulated CPU is set to ARM7500FE (the same CPU as the Bush).

I presume there must be other hardware present in the Bush device which NC OS requires?
I know it has NVRAM and an internal dial-up modem, but would their absence prevent the OS from booting?.

Thanks.

The answer is ‘no’, not at the moment.

I spent some time this week trying to discover why NCOS 1.06 (and 0.10 and 1.11 get stuck at the same point) wasn’t booting. It’s related to another bit of hardware attached to the ARM7500 GPIO pins, triggering something that I’ve not worked out yet.

Though even getting past this is not likely to end up in a usable system. The system is highly reliant on network access and I’m not sure you could bodge NCOS to accept EtherRPC interface instead of the onboard modem/nic.

I’m only working on this for fun, not any practical reason :)

NCOS 1.06 booting after the POST was fudged to not care about the results. Not exactly useful, but at least we should fix it properly :D

Very cool nonetheless :)
Did you modify the ROM image, or the RPCEmu code, or both?

It’s a modification of the rom image, patching a couple of instructions. Though we do this in-emulator, detect the rom image being loaded is an NCOS we know about and patch the copy we load into memory (rather than editing the version on disc).

The failure of the POST test on an NC causes the LED on the front of the box to flash for ever (rather than output the test code by short/long pulses like on the risc pc)

Of the two POST failures that were detected, one looks fixable, but the other relies on too precise timing to emulate, so to support NCOS variants we may always need to patch the rom images.

I’m not sure you could bodge NCOS to accept EtherRPC interface instead of the onboard modem/nic.

If you were to rename EtherRPC to EtherN and put it in the podule ‘ROM’ with a higher version than the one in the system ROM image, it would trump the system one, wouldn’t it? It would need to provide the en0 network device as that’s probably hardcoded somewhere, maybe also fake up the podule descriptions to look like the EtherN podule. Then NCOS wouldn’t notice the difference?